1. Field of the Invention
This invention relates to holding means for a glass substrate formed with a semiconductor thin film element and a radiation photographing apparatus for applying radiation to an object to thereby obtain the radiation image of the object.
2. Related Background Art
Apparatus for applying radiation to an object and detecting the intensity distribution of the radiation transmitted through the object to thereby obtain the radiation image of the object have heretofore been widely utilized in the fields of industrial non-destruction inspection and medical treatment and diagnosis. The radiation image of such an object is photographed by a combination of a fluorescent plate emitting fluorescence by radiation or an intensifying screen and silver salt film. That is, radiation is applied through the object, and the radiation is converted into visible light by the fluorescent plate and a latent image is formed on the silver salt film, whereafter this silver salt film is chemically treated and a radiation image is photographed as an analog photograph.
On the other hand, by the advance of digital technology in recent years, a radiation image is converted into an electrical signal, and this electrical signal is image-processed, and thereafter is reproduced as a visible image in a CRT or the like to thereby obtain a radiation image of high quality. As an apparatus for converting this radiation image into an electrical signal, there is, for example, a film digitizer for photographing by a combination of a fluorescent plate and silver salt film, and applying light to a radiation image recorded on radiation photographic film obtained, photoelectrically reading the light transmitted through the radiation photographic film by a CCD or the like, and converting it into an electrical signal.
Also, owing to the advance of the semiconductor process technology in recent years, it has become possible to make a solid photodetector in which amorphous semiconductor film is sandwiched by and between glass substrates and solid photodetector elements by semiconductor thin film comprising transparent electrically conductive film and electrically conductive film are arranged in the form of a matrix, and there has been proposed radiation detecting means in which this solid photodetector and a scintillator for converting radiation into visible light are layered.
By radiation transmitted through an object being applied to this radiation detecting means, the radiation is converted into visible light by the scintillator, and this visible light is detected as an electrical signal by the photoelectric converting portion of the solid photodetector elements. This electrical signal is read out from each solid photodetector element by a predetermined reading-out system, and is A/D-converted, whereby a radiation image signal is obtained. This signal is subjected to various signal processings by an image signal processing apparatus, whereafter it is reproduced as a radiation image by reproducing means such as a CRT, and is utilized for image reading diagnosis.
Chest photographing directed to the diagnosis of chest diseases is nowadays effected by the use of a screen film system comprising a combination of an intensifying screen and film, but since chest photographing requires a film of a large area, use is generally made of large film of 14 inches.times.14 inches or 14 inches.times.17 inches. Accordingly, when chest photographing is to be effected by the use of radiation detecting means comprising a combination of a scintillator and solid photodetector elements, it is necessary to form a solid photodetector element on a glass substrate of a large area such as 14 inches.times.14 inches, 14 inches.times.17 inches or greater by the photolithography method, and make radiation detecting means.
However, generally, quartz glass having a thickness of 1.1 mm is used as the glass substrate, and quartz glass having a smaller thickness of 0.7 mm is sometimes used for lighter weight, and in order that by the use of radiation detecting means in which amorphous semiconductor film is sandwiched between such fragile thin glass substrates of a large area of 14 inches.times.17 inches or greater and solid detection elements comprising transparent electrically conductive film and electrically conductive film are arranged in the form of a matrix, a radiation photographing apparatus may be embodied and used in the field of medical treatment, a packaging form sufficiently taking environmental resistance into account, particularly, holding means for reliably holding the fragile glass substrate with shock resistance and vibration resistance taken into account becomes necessary.
Particularly, when with a radiation photographing apparatus carried on a vehicle, medical examination is to be effected at various locations, more excellent shock resisting and vibration resisting characteristics are required in order to satisfy the performance as radiation image detecting means even if the apparatus undergoes the vibrations during the movement of the vehicle, and particularly the vibrations and shocks on bad roads.
In the conventional art, however, there is no specific proposition of holding means or the like excellent in shock resistance and vibration resistance and moreover, glass is extremely small in coefficient of thermal expansion as compared with metals and therefore, the influence of thermal deformation need be sufficiently taken into consideration. That is, if the glass substrate is fixed to a metallic mounting substrate, stress will be applied to the glass substrate due to changes in the environmental temperature because glass and the mounting substrate extremely differ in coefficient of thermal expansion from each other, and in the worst case, there will arise the problem that the destruction of the glass substrate will result.